Recently, a mobile radio terminal such as a mobile phone increases its functionality. The increase of the functionality requires the mobile radio terminal, to include various antennas depending on services provided such as one seg (Japanese terrestrial digital broadcasting service for mobile devices), the Global Positioning System (GPS), Bluetooth (registered trademark), a wireless Local Area Network (LAN), and a Frequency Modulation (FM) transmitter, in addition to a cellular antenna. A monopole antenna has been disposed in mobile radio terminals. In a monopole antenna, a substrate functioning as the ground (GND) is a part of the antenna. Accordingly, even if an antenna element is small, a large gain may be obtained with the size of a substrate. A monopole antenna is therefore suitable for a small apparatus such as a mobile radio terminal.
In order to obtain a good characteristic of a monopole antenna, it is desired that an antenna element is mounted as far as possible from the substrate, that is, the monopole antenna is usually disposed at a corner of a housing of the mobile radio terminal. However, when many antennas, such as ones described above, are disposed in a mobile radio terminal, it is difficult to dispose all of these antennas at the corner.
Since the Multiple Input Multiple Output (MIMO) technique is employed in Long Term Evolution (LTE) that is the following-generation communication standard, a sub-antenna designed for reception is further needed. Accordingly, a space required for placement of various antennas may be becoming insufficient. As a technique for solving the space for placement, it has been proposed that antennas may be configured without a conflict between a monopole antenna and a space for placement thereof. As one of these antennas, a notch antenna is known which includes a slit (a notch) in a substrate functioning as an antenna.
For example, it has been proposed a method of changing the resonant length of a notch antenna having a slit of 0.2λ, in a substrate. It has been also proposed a method of broadening the frequency band of a notch antenna having a slit of 0.25λ, in a substrate. Here, λ, represents a wavelength of a frequency used. For example, 0.2λ, corresponds to approximately 30 mm long in the 2 GHz band and to approximately 25 mm long in the 2.4 GHz band. Therefore, it seems easy to dispose the notch antenna in the mobile telephone including the substrate with a size of approximately 90 mm×approximately 45 mm. The notch antenna for a wireless mobile terminal is described, for example, in Japanese Laid-open Patent Publication Nos. 2004-032303 and 2004-056421 are examples of related art.